1. Field of the Invention
The present invention relates to an improved audiometer system which is entirely operable by the user whereby he can self-test his hearing acuity for different frequencies without the assistance of an operator for adjusting the test instrument or for recording the user's responses.
2. Description of Prior Art
Known audiometers are of two main types: the manual and the so called automatic type. In the manual system and method of auditory testing, a skilled operator adjusts the audiometer controls, thereby sending a plurality of audio signals either through earphones, loudspeakers or bone vibrators, to a subject generally sitting in a quiet room. The subject is requested to signal to the operator, either by activating a switch connected to a pilot light, or by raising his hand or by any other visible or audible means, whenever he has heard the sound being sent to him. The operator watches for and interprets the subject's responses and translates them into written information on a chart, this information being represented by a graph called the audiogram which represents the threshold of hearing of the subject for a plurality of audio frequencies.
In the automatic method known as the Bekesy method of auditory testing, the audiometer presents to the subject automatically changing tone frequencies while the intensity of the signal is controlled by the subject by means of a pushbutton switch activating a motor controlling the motion of an intensity attenuator. The subject's responses are also automatically recorded by means of a writing pen moving over a chart as the test progresses. While the Bekesy method is considered by those skilled in the art of audiology as a major advance, it still requires the presence of a skilled operator and the use of rather sophisticated mechanical systems.
A further method of auditory testing has been proposed in which a computer is used to present the tones to the subject in a programmed sequence and record his responses. Reference is made to U.S. Pat. No. 3,809,811 and Canadian patent 950,106. In this type of instrument, the triggering of different intensities and frequencies by the programming circuit is entirely dependent upon the feedback from the subject's responses, through his actuation of a "YES" button, but calling for a relatively complex electronic circuitry.
There exists in industry a need to have an equipment which allows a rapid test of hearing at the time of hiring a new employee to establish his basic status of hearing thereby warning the employer of any hearing loss that may already be present and possibly gone undetected previously and protecting the employer against later claims of hearing loss that would be attributed to his industry's noise. It must be possible to execute such a pre-employment test at the earliest possible time without having to wait for the availability of an operator.
Also, in noisy industrial settings there exists a need to administer periodical hearing tests to employees with minimum lost time away from work. Such a requirement is not easily possible to fulfil with instruments of prior art which usually have to be installed in quiet rooms away from the work premises.
In audiometric methods of prior art, it is quite possible for the subject being tested to deliberately give false responses which might be interpreted by the operator as reflecting the true condition of the hearing acuity of the subject. For instance, new job applicants in industry who are already partially hard of hearing might try to falsify the test by pretending that they heard all the tones presented to their ears, by fear of not being employed if the employer was made aware of their true hearing loss. On the other hand, old employees might pretend of being more hard of hearing than they are in reality, in the hope of obtaining compensation for industrial hearing loss.